Re: [DNA-BOF] Initial Reading List ideas for DNA

[Greg Daley <greg.daley@eng.monash.edu.au>]

Hi Alper,

Alper Yegin wrote:
> Hello,
> 
> Here are two more drafts that are relevant to this work.
> 
> http://www.yegin.org/alper/draft-manyfolks-l2-mobilereq-02.txt
> 
> This work was originally driven by the Mobile IP fast handovers work. We
> made an attempt to formally define link-layer triggers (so called hints in
> Bernard's document) in an abstract form. Their details differ among
> link-layer technologies, but a uniform abstraction is needed from IP
> perspective. Potential consumers of these triggers are discussed in the
> document.

There's certainly a lot of value in L2 'Link UP' triggering on the
attaching host.  We've used this trigger to solicit an RA
with a FastRA capable router in very short time.
I think that section 6.0 summarizes the general benefits of this
technology, without requiring mobility signalling.

The work on context transfer, and oAR/nAR triggering may be more
oriented toward Fast MIPv6 or Seamoby work.

Hasn't this work been picked up by another WG?

> http://ietf.org/internet-drafts/draft-yegin-l2-triggers-01.txt
> 
> This draft proposes a protocol that conveys the link-layer triggers when the
> trigger is generated on one IP node and consumed in another. Example
> scenario is WLAN APs connected to access routers. If the access router wants
> to know when a host connects or disconnects, it needs to be notified by the
> AP.

I agree that the presence of triggers at the AP provides some
incongruity, which samsung's FRD attempts to solve (through RA caching).
Has there been any discussion about the possibility of using AAA
proxying for transferring L2 triggers between APs and ARs?

Is there a value in developing a separate protocol? I was wondering
if it was valid to configure APs to use the AR as a AAA proxy.
This would provide some trust (validation by the AR's AAA service)
in allowing APs to send triggers.



> I think the relevance of link-layer triggers to DNA comes from this: We can
> develop some heuristics for hosts to consume some network layer information
> (such as DHCP info, router advertisements, ND or ARP results) to determine
> if it has moved. Using link-layer triggers would not only enhance the
> perfomance of these mechanisms, but also help increase the confidence of the
> hosts in such determinations.


I'm certainly interested if Triggering systems may be used to
assist attachment detection.  I still think that any communication
between the attaching host and the access network will have to
use existing mechanisms though.

Given this premise, I think that DNA would have to work even
without L2 hints...

About using L2 triggers to free up resources, an analogous
triggering may be applicable for upper layer sessions, similar to
the work done by Spencer Dawkins on TCP.

I'm thinking that L2 triggering may be just a part of the solution
though.  Once the link identity has been determined (for example,
if we know we have attached to a network where the current address
is no-longer valid), then host internal signalling may be
provided to free ND caches, TCP sessions &etc.

There wouldn't be direct correspondence between L2 and upper layers
except through Network Attachment Detection.  I think that
we would have to try to develop a robust enough mechanism for the
detection that it could be relied upon even without the L2 trigger.
(Though it may not be so fast).

Of course, once we start talking about this, there's always the
possibility that the work could be described as "Implementation
Specific".  It may be possible to provide information to implementors
though how this may be done.


> Another angle on this work is, we might also consider the network side for
> assisting network attachment detection. If the network is made aware of
> arrival of a new host, it might provide additional hints to the host.

Sorry to self-advertise here, but we've done some work on
identifying the link in RA messages, which provides a strong
hint to attaching devices about the validity of their configuration.

This works without requiring L2 trigger support.

http://www.ietf.org/internet-drafts/draft-pentland-mobileip-linkid-00.txt

In the case where the network knows about the attachment,
it can send an RA from an AP (Cached) or from the AR (after trigger from
AP).  If it contains a LinkID, it may be possible to
provide unambiguous detection of attachment with just the RA message.

> Finally, while detecting network attachment is important for host to take
> actions to restore IP-layer connectivity, detecting detachment of a host is
> also important/useful for networks in order to at least free up resources.
> Do we consider this in scope?

I'm not sure yet!

There seems to be a lot which people are interested in.

Maybe we can talk about what we need to achieve first,
and then describe what means are considered to have good
potential.

Experience in WGs which have attempted to define some
of these methods previously (for example mobileip) may
be beneficial.

At this stage, collecting a reading list is not about
how to solve the problems, but talking about previous work,
so that people can gain a picture of what has been happening
in areas which may complement their own interest.

Thanks for the references.

Greg